1. To make the meatballs, mix together the onion, garlic, lamb, egg yolk, parsley and seasoning until well blended.

2. Mould mozzarella into balls approximately the size of the end of your thumb.

3. Divide the mixture into 20 pieces and mould into balls, each with a piece of mozzarella in the centre. Place on a baking sheet, cover with clear film and chill for 30 minutes.

4. Heat the oil in a large frying pan and place the meatballs in it.

5. Fry the meatballs for about 10 minutes, turning occasionally, until browned on all sides. Drain the pan of any excess fat, without tipping the meatballs out.

6. For the sauce, add the passata, basil, garlic and seasoning to the pan and bring to the boil. Cover and simmer for 20 minutes until the meatballs are tender.

7. Meanwhile, bring a large pan of salted water to the boil. Add the pasta and cook according to the packet instructions until it is just al dente. Drain thoroughly and divide it among four serving plates. Spoon over the meatballs and some of the sauce. Garnish each portion with a fresh rosemary sprig and serve immediately with plenty of freshly grated Parmesan cheese.

**Tip:

Passata is available in jars, tins or cartons from specialist Italian grocery stores and most large supermarkets. It is made from sieved tomatoes so you could make your own.

(The meatballs can be made a day in advance. Place them on a baking sheet, cover with clear film and chill.)